Rotatable cutting tools are used in conjunction with a machine used to break up (or cut) a substrate such as coal, rock, asphalt pavement, asphaltic concrete, concrete or the like. In its very basic aspects, such a machine includes a driven member (e.g., a chain, a wheel or a drum), a holder either directly or indirectly mounted to the driven member, and a rotatable cutting tool rotatably held in the holder. It is the cutting tool that impinges the earth strata so as to break it into pieces and chunks upon impact.
Rotatable cutting tools and the holders operate in a high wear environment. These components inevitably fail due to the severity of the operating conditions; e.g. gritty, dusty and highly abrasive. While it is expected that the cutting tools experience wear, the ability of the cutting tool to rotate about its central longitudinal axis during operation generally prolongs the useful life of the cutting tool. Rotation promotes more even wear about the tool. It can thus be appreciated that features of the cutting tool or cutting tool assembly that facilitate the rotation of the cutting tool during operation are beneficial to the operation of the cutting tool (and cutting tool assembly) and the overall operation of the cutting machine.
As known to those skilled in the art, the useful life of the holder is much longer than the useful life of the cutting tool. A holder is often referred to as a part of a block. Accordingly, the term “holder” refers herein to a portion of a block or a block which holds a cutting bit. Each block is intended to accommodate many changes of cutting tools before the block must be changed. In order to reduce the wear on the forward face of the block and fretting between the block and the cutting bit, a wear sleeve may be used in conjunction with cutting tool and holder. The wear sleeve generally has a forward portion and shank and is positioned between the cutting tool and holder. The wear sleeve protects the block from wear and is removably mounted in the holder.
Although it is beneficial to promote rotation of the cutting tool, rotation of the wear sleeve in the bit holder is not desirable. As dust and/or debris works in between the bit holder and the wear sleeve, rotation of the wear sleeve encourages abrasion between the bit holder and the wear sleeve.
One such cutting tool that teaches a protective wear sleeve is shown and described in U.S. Pat. No. 7,270,379 to Stehney. Stehney '379 teaches a sleeve mounted in a holder block which utilizes a stepped configuration on the shank of the sleeve to create an interference fit between the holder block and the sleeve. The interference fit retains the sleeve within the holder block and prevents rotation within the sleeve of the holder block.
Another cutting tool that uses a protective wear sleeve is shown and described in U.S. Pat. No. 5,106,166 to O'Neill. O'Neill '166 teaches a wear sleeve with an index pin between the collar of the wear sleeve and the forward face of the block. O'Neill '166 also prevents rotation of the wear sleeve by utilizing a pin through an aperture through a shank of the block. The pin passes through the block and contacts a flat surface machined into the wear sleeve. In another embodiment, O'Neill '166 teaches non-rotation of the wear sleeve by using a hexagonally-shaped sleeve shank and block bore.
U.S. Pat. No. 5,273,343 to Ojanen teaches a non-rotatable wear sleeve. Ojanen '343 describes a wear sleeve for mounting a cutting tool in a bit holder. The deformed sleeve has one end shaped as an ellipse. The deformed sleeve is then force fit into a bore in the block and is retained therein in a non-rotating manner by friction. U.S. Pat. No. 5,303,984 to Ojanen teaches a non-rotatable sleeve for use in a block. Ojanen '984 teaches a diametrically compressible sleeve mounted in the bore of the block. The sleeve has an axial slot which allows it to be compressed from a diameter larger than the given diameter before insertion into a bore of the block and a compressed diameter substantially matching the given diameter after insertion into the bore of the block.
Numerous other teachings disclose similar devices and methods. Each teaching suffers from one or more of the following deficiencies. The wear sleeves must be replaced regularly as they wear out so convenient installation and extraction is important. However, the protective sleeve must also be secured in the bit holder so as not to be knocked loose by loads and torques that occur during normal operation of the cutting machine.
Another cutting tool that uses a protective member is shown and described in U.S. Pat. No. 6,508,516 B1 to Kammerer. The '516 Patent discloses a ring that includes a tab. The tab engages grooves in a holder so that the ring does not rotate relative to the holder. At the beginning of a milling cycle, the structure disclosed in U.S. Pat. No. 6,508,516 to Kammerer would be expected to provide a non-rotatable ring; however, over time the structure may be susceptible to problems. One such problem is that the groove that engages the tab may become clogged with debris. Obviously, this condition could compromise the integrity of the connection between the tab and the groove and result in the loss of the non-rotatable feature of the ring. Another problem is that over the course of operation the tab is exposed along the side of the tool so as to be susceptible to wearing away. The erosion of the tab could compromise the integrity of the connection between the tab and the groove and result in the loss of the non-rotatable feature of the ring.
The present invention has been developed in view of the foregoing.